What does it mean if early Atlantic hurricane season is relatively calm?

When Tropical Storm Andrea made its 12-hour appearance in the middle of the northern Atlantic Ocean earlier this week, it ended the longest wait for a named storm in the basin since the 2014 season.

It developed in open waters west of the Azores and hundreds of miles east of Bermuda. It was only briefly strong enough to count as a tropical storm, but Andrea nonetheless entered the record books as the named storm to occur the farthest northeast during June.

However, Andrea’s brief blip of life doesn’t change expectations for the season. The Atlantic remains off to a somewhat quiet start, while the eastern Pacific keeps the storms coming. Forecasts still expect an above-average hurricane season, with the National Oceanic and Atmospheric Administration forecasting as many as 19 named storms. While the greater meaning of the early season may stir up some debate, history indicates there is no real relationship between early-season Atlantic storms and how active the year ends up.

“June, and even July, are usually fairly quiet,” said Brian McNoldy, senior research associate at the University of Miami’s Rosenstiel School. “Seasonal forecasts for above-average activity could still easily come to fruition.”

Monkey off the back in the Atlantic

Preseason outlooks mostly called for another in a lengthy string of active years for Atlantic hurricanes. The season officially began June 1 – but there were no storms to be found until Tuesday.

Andrea became the latest first tropical or subtropical storm of the season since Arthur more than a decade ago. In 2014, we had to wait until July 1 for a storm to be named in the Atlantic Ocean.

In many instances in the past two decades, storms were named before the official beginning of the season. Few of those storms amounted to much.

There are also plenty of examples of years with slow starts that ended up active and destructive.

In 1998, Alex wasn’t named until the end of July, starting a season that ended up among the deadliest on record, with 10 hurricanes including the catastrophic Category 5 Mitch. Again in 2004, Alex held off until the start of August, before a slew of major hurricanes slammed Florida and the Gulf Coast.

Why the lack of storms?

The dearth of storms might be somewhat overstated. The first named storm of the Atlantic season averages an arrival around June 20 in the current climate. The first hurricane tends to come along by Aug. 11.

Even in more active years to date, Atlantic Ocean storm activity is typically minimal.

There is also no correlation between how a season begins and how active it turns during prime time. Although hurricane seasons last half a year in entirety, most are historically quite regular, with the brunt coming over a roughly eight-week period from mid-August to mid-October.

While fewer early-season storms may mean a lower chance of the year reaching the highest end of named storms – the record is 30 in 2020 – the intensity of any coming storms and the general number of strong storms are unaffected.

McNoldy said that while there is no ongoing El Niño – a climate pattern that affects global weather – which usually portends elevated Atlantic Ocean tropical activity, water temperatures have also lately trended cooler than average across much of the basin. The relatively cooler waters include the region of the tropical Atlantic Ocean known as the Main Development Region, which is where a majority of storms form.

It is still early for that zone to light up with potential, but the cooler sea surface readings are still unusual compared with recent years.

Storm expectations do begin to rise in July, but major hurricanes are still relatively uncommon during that month. Just last July, Hurricane Beryl became the earliest Category 5 on record in the Atlantic after forming in the Main Development Region.

Eastern Pacific still stormy

On the other side of Central America, the eastern Pacific Ocean keeps churning out storms at a record pace. Close on the heels of an earliest-on-record Category 4 landfall in Mexico with Erick, another storm is poised to develop in the short term.

But there may be a connection between the hyperactive eastern Pacific and the relatively tranquil Atlantic.

McNoldy pointed to several links.

“When the east Pacific is abnormally active, upper-level winds from the storms’ exhaust increases the wind shear over the neighboring western Atlantic,” he said. “It also induces subsidence, which suppresses cloud development in the same areas.”

For now, the outlook for the first half of July keeps expectations low in the Atlantic basin. Below-average rainfall probability is anticipated by the Climate Prediction Center for much of the Main Development Region, including the Caribbean Sea.